1. Technical Field
This invention relates in general to digital communications and in particular to the transmission and processing of data streams. Still more particularly, this invention relates to the processing of nested mixed data objects within a data stream.
2. Background Art
In traditional revisable document architecture systems, the mixing of data from diverse data types has been limited to that which may be accomplished by placing the data into spaces that exist within a document layout. This placement rarely provides the granularity of positioning which is needed to handle mixing of elements from one data type into the coordinate space of a second data type. Examples of such a mixture is the utilization of text to satisfy the requirements of labeling the axes of graphic drawings or the drawing of rectangles around text in a prose section. These data instances are generally referred to as "special cases" because it is rare that the full data processing potential normally associated with text data is available for utilization in the first example and with graphics data in the second example. For example, text which has been inserted into a graphic document to label the axes thereof is generally not available for word processing or spell checking by a text editor application.
Additionally, placement of a mixed data type at the layout level also generates a problem due to the possibility of having to transform between different coordinate systems and units of measure, such as those provided by the data objects for the diverse data type elements which must be positioned into the data object space. Such positioning is further complicated by the absence of an explicit means to preserve the current position established in the coordinate space of a data object.
Correlation of objects by position specification has been attempted by utilizing an architected solution which directly mirrors these relationships. The utilization of a Document Content Architecture (DCA), which provides a wide variety of positioning capabilities has been attempted to satisfy the document composition requirements that exist in such mixed object documents. Although each data object in this system has its own coordinate space definition which may be offset from its associated object area, the data object coordinate space and its associated object area are identical in terms of orientation, extent and size and origin so that a data object may be positioned relative to all coordinate spaces in which the data object may be nested. While this technique represents one attempt at solving the aforementioned problem, it does not address the additional complexities which occur when multiple mixed data objects are combined within a data stream. For example, the environment of a particular data object may include additional features beyond the coordinate system; such as, unit of measure, color, or font.
Still another attempt at permitting a data stream to include multiple mixed data objects utilizes the establishment of a composite environment which is created as an outside environment specification. Thereafter, modifications to this outside environment specification are made by adding or subtracting environment specifications from the specification. While this technique permits a data stream with mixed data objects to more easily specify the environment elements for each object, it does not enhance the capability of the user to efficiently nest a plurality of mixed data objects while passing environment elements from one data object to a second data object.